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Full text of "Practical Organic Chemistry"

PICRIC ACID                                  Ig

PREPARATION   80.

Picric Acid (Trinitrophenol), C0H9(OH)^No!   4                              1 '

XN02    6

Woulfe, 1771 ; Schmidt, Glutz, Bcr^ 1869, 2, 52.                                    * I

* I
25 grms. phenol.                                                                                           l|^

25     „     cone, sulphuric acid.                                                                       \'fl

i QQ     „     (70 c.c.) cone, nitric acid, sp. gr. 1*4.                     -                          j*

25     „     (20 c.c.) fuming nitric acid, sp. gr. 1-5.                                            |'

tf<)

The  phenol  and  concentrated   sulphuric  acid  are  heated                       ,<' i

together in  a ])orcclain basin for a few minutes, until a clear                       V*

solution   of phenol   sulphonic acid is obtained.     It  is diluted.                        '*

with half its volume  of water,   well   cooled, and  then slowly                        4

added, in small quantities at a time, from a tap-funnel, to the                       ^

nitric acid  contained  in  a  flask  (r   litre), and  well shaken.*-                       \f

The liquid assumes a, deep red colour, a considerable rise of                      If

temperature occurs, and red fumes  are   evolved.     When the                       -f*

phenol sulphonic acid has been added, the flask is placed on.                       *d

the water-bath and heated, with the addition of 25 grams fuming-

nitric acid, for i.....2 hours.*    On cooling, picric acid separates

out as a yellow, crystalline mass. It is diluted with water,
filtered at the pump, and washed free from the mother liquor
with cold water. It is then purified by recrystallisation from a
large quantity of hot water acidified with a few drops of
sulphuric acid. Yield, about 30 grains.

CJ l,(011) +1 F,SO., - C0H4(0H).S03H + H20.

C(;Ha(OH)(NOa)3 + 3H20 + H2SO4.                       if
ft
Properties.-—Yellow, prismatic crystals; m. p.   122*5°;   sub-                       ^i
limes on gently heating ; explodes on detonation ; easily soluble
\\\ alcohol and ether ; with difficulty in cold, more readily in                       f|
hot water ; the solution has a bitter taste.
Reactions.— r. To an aqueous solution of picric acid add a
little potassium cyanide solution, and warm. A brown crystal-
line precipitate of isopurpuric acid separates.
2. Add picric acid and a few drops of caustic socla to a dilute
solution of grape sugar, and warm. The liquid turns deep brown.